1. Field of the Invention
The present invention is directed toward the field of building custom memory systems cost-effectively for a wide range of markets.
2. Art Background
Dynamic Random Access Memory (DRAM) is the most popular type of volatile memory and is widely used in a number of different markets. The popularity of DRAMs is mostly due to their cost-effectiveness (Mb/$). The PC main memory market has traditionally been the largest consumer of DRAMs. However, in recent times, other important markets have adopted DRAMs. A report published by De Dios and Associates showed that in 2004, the PC main memory market consumed only 50% of the total DRAM bits.
Several of the non-PC markets use specialty or legacy memories. Specialty memory is typically memory that is not used by the PC main memory but is memory that is designed for one or more niche markets. For example, the PC graphics market uses GDDR (Graphics Dual Data Rate) DRAM. Similarly, some segments of the network infrastructure market use FCRAM (Fast Cycle RAM) or RLDRAM (Reduced Latency DRAM). Legacy memory is typically memory that was used in the past but is not used in that particular market segment now. For example, SDRAM (Synchronous DRAM) was used for PC main memory from ˜1997 to ˜2001 but is no longer used today for PC main memory. Instead, most cellular phones and handheld (or mobile) devices use SDRAM today.
Bringing a new DRAM architecture into the market requires significant investment of time and money. For example, it typically takes 4 years for JEDEC to approve a new DRAM architecture. DRAM makers must then spend hundreds of millions of dollars to productize the new architecture. Unless the investment is amortized over an extremely large number of devices, the cost of the new devices will be high. In addition, the DRAM makers have optimized their manufacturing flow for high volumes. Any deviation from the norm disrupts the flow. This is the reason why specialty and legacy memory typically carry a price premium over memory used by the PC main memory market (which is usually referred to as commodity memory).
Given the time and money required to bring a new DRAM architecture into the market, it is obvious that the industry does not have the luxury of being able to define a DRAM architecture that exclusively meets the needs of the smaller markets for DRAMs. For example, it is difficult for the DRAM makers to cost-effectively produce a DRAM that perfectly meets the needs of the cell phone market. Therefore, it is even more difficult for each cell phone maker (e.g. Nokia or Motorola) to design DRAMs tailor made for its phones. So, cell phone designers are forced to choose the DRAM architecture that is least objectionable from their perspective. Hence the selection of SDRAM for cell phones.
This situation will become even worse in the future. Most analyst projections show that not only will DRAM usage expand rapidly into newer markets but also that the DRAM bit consumption growth rate will be higher for non-PC markets. The needs of these markets are quite different from the needs of the PC main memory market. Clearly, there is a need in the market for a way to quickly and cost-effectively build custom memory that is tailor made for a customer's exact needs.